Side channel compressor

ABSTRACT

The invention concerns a side channel compressor for compressing a gas, the side channel compressor comprising a housing ( 3 ), a side channel ( 30 ) located in the housing ( 3 ) for compressing a gas, a gas inlet opening which is formed in the housing ( 3 ) and is in flow connection with the side channel ( 30 ) for introducing a gas to be compressed, a gas outlet opening ( 32 ) formed in the housing ( 3 ) for discharging the gas to be compressed from the side channel ( 30 ), the gas outlet opening ( 32 ) being in flow connection with the gas inlet opening ( 31 ) by way of the side channel ( 30 ), and a impeller ( 2 ) mounted for rotary drive in the housing ( 3 ), the impeller ( 2 ) having at least two impeller blades ( 1 ) disposed in the side channel, wherein at least one impeller blade ( 1 ) has a flow recess in its free edge region ( 47 ).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention concerns a side channel compressor for compressing a gas.The invention therefore concerns a work machine for compressing gases,such as air or technical gases.

2. Background Art

The operation of the side channel compressor results in a broadbandsound spectrum. In conventional side channel compressors, tonal soundcomponents occur at certain frequencies of the side channel compressorwhich are extremely annoying if they differ from the broadband soundspectrum by more than 7 dB.

SUMMARY OF THE INVENTION

It is the object of the invention to provide a side channel compressorwhich ensures a particularly silent operation.

This object is achieved by a side channel compressor for compressing agas the side channel compressor comprising a housing; a side channellocated in the housing for compressing a gas; a gas inlet opening formedin the housing which is in flow connection with the side channel forintroducing a gas to be compressed; a gas outlet opening formed in thehousing for discharging the gas to be compressed from the side channel,the gas outlet opening being in flow connection with the gas inletopening by way of the side channel; and an impeller which is mounted forrotary drive in the housing and has at least two impeller bladesdisposed in the side channel, wherein at least one impeller blade has atleast one flow recess in its free edge region. The essence of theinvention is that at least one flow recess is provided in the free edgeregion of at least one impeller blade of the side channel compressor.The free edge region is the region which is located in the side channeland which may be surrounded by the gas to be compressed. The at leastone flow recess or the amount of gas flowing through this flow recess,respectively, reduces gas turbulence structures and/or periodic gas flowstructures occurring at the trailing side of the impeller blades. Thisensures a particularly silent operation of the side channel compressor.

The following is a detailed description of several preferred embodimentsof the invention by means of the enclosed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a side view of a side channel compressor and of a driveflange-mounted to the side channel compressor, the Figure showing apartial longitudinal sectional view of the side channel compressor;

FIG. 2 shows a front elevation view of the side channel compressor shownin FIG. 1;

FIG. 3 shows a front elevation view of the side channel compressor shownin FIG. 2 with its housing cover taken off;

FIG. 4 shows a schematic view of an inventive impeller according to afirst embodiment of a side channel compressor;

FIG. 5 shows a substantially rear view of an impeller blade of theimpeller shown in FIG. 4;

FIG. 6 shows a schematic view of an inventive impeller according to asecond embodiment;

FIG. 7 shows a substantially rear view of an impeller blade of theimpeller shown in FIG. 6;

FIG. 8 shows a schematic view of an inventive impeller according to athird embodiment;

FIG. 9 shows a substantially rear view of an impeller blade of theimpeller shown in FIG. 8;

FIG. 10 shows a schematic view of an inventive impeller according to afourth embodiment;

FIG. 11 shows a substantially rear view of an impeller blade of theimpeller shown in FIG. 10;

FIG. 12 shows a schematic view of an inventive impeller according to afifth embodiment;

FIG. 13 shows a substantially rear view of an impeller blade of theimpeller shown in FIG. 12;

FIG. 14 shows a schematic view of an inventive impeller according to asixth embodiment;

FIG. 15 shows a substantially rear view of an impeller blade of theimpeller shown in FIG. 14;

FIG. 16 shows a schematic view of an inventive impeller according to aseventh embodiment;

FIG. 17 shows a substantially rear view of an impeller blade of theimpeller shown in FIG. 16; and

FIG. 18 shows a schematic view of an inventive impeller according to aneighth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A side channel compressor shown in FIGS. 1 to 3 for compressing a gascomprises an impeller 2 which is provided with impeller blades 1 and ismounted in a housing 3 for rotation about a horizontal centrallongitudinal axis 4. A conventional drive 6 serves for rotary drive ofthe impeller 2 in the direction of the arrow 5. The gas is thustransported through the housing 3 in the direction of the arrow 5 aswell.

The housing 3 comprises a housing body 7 and a demountable housing cover8 which are joined together according to FIGS. 1 and 2 so as to enclosethe impeller 2 comprising the impeller blades 1 which is drivable forrotation and is disposed on a drive shaft 9 for co-rotation therewith.

The impeller 2 is provided with a single blade ring and is designed likea disk. The impeller 2 comprises an inner impeller hub 10 with a centralcircular hub bore 11. The impeller hub 10 is formed by an inner hub foot12 which radially outwardly delimits the hub bore 11, and by a radialcircular hub washer 13 adjoining the hub foot 12. Moreover, the impeller2 comprises a radial outer carrier ring 14 which adjoins the outside ofthe hub washer 13 and overlaps with both sides of said hub washer 13 inthe direction of the central longitudinal axis 4. The carrier ring 14carries a multitude of radially projecting impeller blades 1 which aredistributed in the circumferential direction. In this embodiment, atotal of 52 individual impeller blades 1 are provided which arepreferably arranged equidistantly so as to have an angular distance fromone another, relative to the central longitudinal axis 4, that amountsto approximately 7°. Thus, 6 to 7 impeller blades 1 are disposed atevery 45°. The hub foot 12, the hub washer 13 and the carrier ring 14form an integral cast part.

The terms “axial” and “radial” used in-here are relative to the centrallongitudinal axis 4. The terms “inner” and “outer” are relative to thecentral longitudinal axis 4 as well. The term “inner” means that aninner region is nearer to the central longitudinal axis 4 than an outerregion.

The central hub bore 11 may receive the drive shaft 9. A conventionalparallel-key connection is provided between the drive shaft 9 and thehub foot 12 so as to transmit the torque generated by the drive shaft 9to the impeller hub 10 for rotating the impeller 2.

The housing body 7 comprises a central hub portion 15 which radially andaxially delimits a partial hub receiving space 16. A central shaft bore17 passes through the hub portion 15 and opens into the partial hubreceiving space 16. An annular side wall 18 adjoins the hub portion 15,said annular side wall 18 extending radially outwardly from the hubportion 15. A circumferential channel portion 19 adjoins the outside ofthe side wall 18. The hub portion 15, the side wall 18 and the channelportion 19 form an integral cast part which forms the housing body 7.Rib webs 20 extending in a spoke-like manner are provided on the outsideof the housing body 7 which considerably increase the stability of thehousing body 7. Moreover, screw bosses 21 project radially outwardlyfrom the side wall 18.

The housing cover 8 is secured to the housing body 7 by means of severalconnecting screws 22 and comprises a central hub portion 23 whichradially and axially delimits a partial hub receiving space 24. Aradially outwardly extending annular side wall 25 adjoins the hubportion 23. A circumferential channel portion 26 is attached to theoutside of the side wall 25. A rolling-element bearing 27 for the driveshaft 9 is disposed in the hub portion 23. The hub portion 23, the sidewall 25 and the channel portion 26 form an integral cast part whichforms the housing cover 8. Likewise, rib webs 28 extending in aspoke-like manner also project from the outside of the side wall 25 soas to reinforce the housing cover 8.

The housing body 7 and the housing cover 8 are joined together such thatthe two partial hub receiving spaces 16, 24 define a hub receiving space29 between each other, and the two channel portions 19, 26 define a sidechannel 30 between each other for compression of the gas. The two sidewalls 18, 25 are parallel but spaced from one another. The side channel30, which is spaced from the central longitudinal axis 4, extendsannularly about the central longitudinal axis 4 and is delimited by thechannel portions 19, 26.

An axial gas inlet opening 31 projecting into the side channel 30 isformed at the bottom of the housing cover 8. Further provided at thebottom of the housing cover 8 is an axial gas outlet opening 32 which isin flow connection with the side channel 30 as well and is adjacent tothe gas inlet opening 31. A projecting gas inlet connector 33 isconnected to the gas inlet opening 31 while a gas outlet connector 34projecting in a likewise manner is connected to the gas outlet opening32. An interceptor 35 is disposed in the side channel 30 between the gasinlet opening 31 and the gas outlet opening 32.

The hub foot 12 of the impeller 2 is disposed in the hub receiving space29 defined by the hub portions 15, 23, with the drive shaft 9 passingthrough the hub bore 17. The drive shaft 9 is provided with a freebearing journal 36 at its end which is mounted for rotation in therolling element bearing 27 in the housing cover 8. The rolling elementbearing 27 is provided with an inner ring 37 connected to the bearingjournal 36 and an outer ring 38 connected to the housing cover 8, withthe rings being separated by rolling elements—in the shape of bearingballs 39—disposed therebetween. The inner ring 37 is shrunk onto thebearing journal 36 for co-rotation therewith while the outer ring 38 isattached to the housing cover 8 in a non-rotational manner. The hubwasher 13 of the impeller 2 extends radially outwardly from the hub foot12 between the spaced-apart side walls 18, 25 of the housing 3. Thecarrier ring 14 and the impeller blades 1 are located in thecircumferential side channel 30. A certain portion of the foot of thecarrier ring 14 is positioned in an outwardly open recess 40 which isformed in the channel portions 19, 26 next to the side walls 18, 25.

The side channel 30 has a free cross-sectional area which is availablefor transporting the gas and is approximately perpendicular to the arrow5. Said cross-sectional area tapers from a cross-sectional area A_(E) atthe gas inlet opening 31 to a cross-sectional area A_(A) at the gasoutlet opening 32 such that A_(A)<A_(E). The side channel 30 may howeverhave a constant cross-sectional area as well.

The side channel 30 has a radial height S. The drive 6 is an electricmotor which is detachably connected to the outside of the housing body7. To this end, several fastening screws are provided which are screwedin the screw bosses 21 at the housing body 7.

In order to ensure that the unit formed by the side channel compressorand the drive 6 is securely installed, support feet 41 are formed at thebottom of the side channel compressor while support feet 43 are formedat the bottom of a carrier body 42 as well, wherein the carrier body 42is connected to the housing body 7 by means of screws and carries thedrive 6.

A vertical plane E runs through the central longitudinal axis 4 andintersects the side channel compressor in a vertically symmetricalmanner or centrally along the length, respectively.

The impeller blades 1 according to a first embodiment are now describedin more detail by means of FIGS. 4 and 5. Each impeller blade 1 issubstantially designed like a plate and has a substantially rectangularshape with a corresponding contour. The impeller blades 1 are designedidentically and symmetrically relative to a symmetry plane X which isoriented perpendicular relative to the vertical plane E and runs throughthe center of the hub washer 13. Each impeller blade 1 further has anedge which is composed of a radially outer edge region 45, a radiallyinner edge region 46 opposite thereto, and lateral edge regions 47inter-connecting the outer and inner edge regions. The inner edge region46 is in direct connection with the carrier ring 14 and may also beregarded as the foot area of the impeller blade 1 while the entire edgeregion 45—which may be regarded as the head area of the impeller blade1—is entirely located in the side channel 30 and is orientedsubstantially parallel to the central longitudinal axis 4. The lateraledge regions 47 are substantially parallel to each other and extendsubstantially radially outwardly from the inner edge region 46. The edgeregions 45 and 47 are free, in other words there are no adjacentelements whatsoever. The inner edge region 46, on the other hand, is notfree as it is adjoined by the carrier ring 14. The edge regions 45, 46,47 define a front surface 48 facing in the direction of the arrow 5 anda rear surface 49 opposite thereto, thus facing in the oppositedirection of the arrow 5. Each impeller blade 1 further comprises aninner edge portion 50 adjoining the inner edge region 46 and an outeredge portion 51 adjoining the outer edge region 45. The inner edgeportion 50 extends radially outwardly from the inner edge region 46,while the outer edge portion 51 is slightly inclined forwardly in thedirection of the arrow 5 relative to the inner edge portion 50 forreasons of flow. The outer edge portion 51 also reduces in thicknesstowards the outer edge region 45 when seen in the circumferentialdirection.

The distance between the outer edge region 45 and the inner edge region46 defines a radial height H of an impeller blade 1, wherein the radialheight H of the inner edge portion 50 preferably amounts to between 55%and 75% of the radial height H. The radial height H is present near thelateral edge regions 47. Furthermore, each impeller blade 1 has an axialwidth B which is defined by the distances between the opposite edgeregions 47.

The radial height H of an impeller blade 1 is smaller than the radialdepth S of the side channel 30. The radial height H amounts to betweenapproximately 50% and 75%, preferably to approximately 60%, of theradial depth S of the side channel 30. Moreover, the axial width B of animpeller blade 1 is always considerably smaller than the correspondingaxial width of the side channel 30.

In this embodiment, the lateral edge regions 47 of an impeller blade 1are in each case further equipped with a reduction groove 52 having asubstantially rectangular cross-section, wherein said reduction groove52 is axially outwardly open and is parallel to the outer edge region45. These reduction grooves 52 are not shown in FIGS. 1 to 3. Eachreduction groove 52 opens into the corresponding front surface 48 andrear surface 49 of an impeller blade 1, thus passing through the entireouter lateral side of the impeller blade 1. The opposite reductiongrooves 52 are on a common level in the inner edge portion 50. They arelocated in the lower half of the inner edge portion 50 at a distancefrom the inner edge region 46, with each of the reduction grooves havinga radial height A which amounts to between approximately 5% and 20%,preferably to between 10% and 15% of the radial height H of an impellerblade 1. The axial depth T of a reduction groove 52 amounts to betweenapproximately 2% and 12%, preferably to between 5% and 9%, of the axialwidth B of an impeller blade 1.

The following is a description of an inventive side channel compressor.The drive shaft 9 is set in rotation about the central longitudinal axis4 in the direction of the arrow 5 by means of the drive 6. As it iscoupled to the drive shaft 9 for co-rotation therewith, the impeller 2comprising the impeller blades 1 therefore starts to rotate in thedirection of the arrow 5 as well. Passing close to the gas inlet opening31, the impeller blades 1 draw the gas to be compressed into sidechannel 30 through the gas inlet connector 33 and the gas inlet opening31. The gas located in the side channel 30 is accelerated, by means ofthe impeller blades 1, in the direction of the arrow 5 which may thusalso be referred to as transport arrow. The front surfaces 48 of theimpeller blades 1 face forwardly in the direction of the arrow 5 andserve for the transport of the gas located in the side channel 30.During the transport, the gas is virtually trapped in cells 44 which areinwardly delimited by the carrier ring 14 and by adjacent impellerblades 1 in the circumferential direction. A cell 44 is in particulardefined by the front surface 48 of an impeller blade 1 and the rearsurface 49 of an impeller blade disposed adjacent thereto. The edgeregions 45, 47 are free, thus allowing the gas to flow across or to passby, respectively.

Due to the reduction grooves 52, the respective surface area of thefront surfaces 48 and rear surfaces 49 of the impeller blades 1 issmaller than that of conventional ungrooved impeller blades. Thereduction grooves 52 form flow channels, enabling a part of the gas topass from one cell into another, downstream cell 44 which is located inthe opposite direction of the arrow 5. The reduction grooves 52 thusalso act as lateral flow grooves through which a part of the gas canflow. These reduction grooves 52, or the amount of gas flowing throughthese reduction grooves 52, respectively, lead to a reduction of gasturbulence structures at the trailing side of the impeller blades 1.This in particular reduces the magnitude and intensity of the gasturbulence structures in the side channel 30 and consequently leads to areduction of pressure variations. The operating noise of the sidechannel compressor is reduced as well. At the end of the circulationzone, the compressed gas is discharged from the side channel 30 via thegas outlet opening 32 and the gas outlet connector 34 by way of theimpeller blades 1. The angular path covered by the gas in the sidechannel compressor amounts to approximately 300°. The interceptorprevents the gas transported by the impeller 2 from being carried overfrom the gas outlet opening 32 to the gas inlet opening 31 in the sidechannel 30.

The following is a description of a second embodiment of the inventionby means of FIGS. 6 and 7. Identical parts are referred to with the samereference numerals as the first embodiment shown in FIGS. 4 and 5 to thedescription of which reference is made. Parts that are different indesign but have the same function are denoted by the same referencenumerals with a subsequent a. The impeller 2 a shown in FIG. 6 differsfrom the impeller 1 shown in FIG. 4 with respect to its impeller blades1 a which are again symmetrical relative to the symmetry plane X. Unlikethe impeller blades 1 according to FIGS. 4 and 5, the impeller blades 1a are provided with two spaced-apart, identical reduction grooves 52 ineach edge region 47 a, said reduction grooves 52 being parallel to eachother and to the outer edge region 45. The reduction grooves 52 are ineach case located in the inner edge portion 50 and are disposed oneabove the other. They pass through the entire impeller blade 1 again,thus virtually forming flow channels. The lower reduction groove 52 isdisposed at a distance from the lower edge region 46 while the upperreduction groove 52 is disposed at a distance from the edge portion 51.As far as design, dimension and function of the reduction grooves 52 areconcerned, reference is made to the aforementioned embodiment. Comparedto the aforementioned embodiment, i.e. compared to the impeller blades 1according to the first embodiment, the surfaces 48 a, 49 a of theimpeller blades 1 a are even smaller, and due to the doubling of thereduction grooves 52, approximately twice the amount of gas is able toflow from cell 44 to cell 44. The gas turbulence structures at thetrailing side are reduced even more.

The following is a description of a third embodiment of the invention bymeans of FIGS. 8 and 9. Identical parts are referred to with the samereference numerals as the second embodiment shown in FIGS. 6 and 7 tothe description of which reference is made. Parts that are different indesign but have the same function are denoted by the same referencenumerals with a subsequent b. Unlike the aforementioned embodiment shownin FIGS. 6 and 7, this embodiment is provided with a reduction groove 52in the outer edge portion 51 b as well. Each edge region 47 b isprovided with a total of three identical reduction grooves 52 which arein each case spaced from each other. They are parallel to each other andto the outer edge region 45. The upper reduction groove 52 in the edgeportion 51 b is disposed at a distance from the outer edge region 45.The reduction grooves 52 are disposed one above the other at identicaldistances relative to each other. The impeller blades 1 b are againsymmetrical relative to the symmetry plane X. As far as dimensioning,design and function of the reduction grooves 52 are concerned, referenceis made to the aforementioned embodiment. Compared to the secondembodiment, turbulence structures at the trailing side are reduced evenmore as the additional reduction grooves 52 make the surfaces 48 b, 49 beven smaller, thus enabling more gas to flow through the reductiongrooves 52.

The following is a description of a fourth embodiment of the inventionby means of FIGS. 10 and 11. Identical parts are referred to with thesame reference numerals as the third embodiment shown in FIGS. 8 and 9to the description of which reference is made. Parts that are differentin design but have the same function are denoted by the same referencenumerals with a subsequent c. The only difference to the thirdembodiment according to the FIGS. 8 and 9 is that the reduction grooves52 c have a semi-circular cross-section instead of a rectangular one.They are again axially outwardly open and pass through the entireimpeller blades 1 c. They are disposed one above the other and have amaximum depth that is equal to depth T. Their maximum outside height isapproximately equal to height A. As far as position and function of thereduction grooves 52 c are concerned, reference is made to the thirdembodiment. In this embodiment, the impeller blades 1 c are subject to aparticularly low notch effect. Semi-circular reduction grooves 52 c arealso suitable for the first and second embodiments.

The following is a description of a fifth embodiment of the invention bymeans of FIGS. 12 and 13. Identical parts are referred to with the samereference numerals as the first embodiment shown in FIGS. 4 and 5 to thedescription of which reference is made. Parts that are different indesign but have the same function are denoted by the same referencenumerals with a subsequent d. Unlike the first embodiment shown in FIGS.4 and 5, the lateral edge regions 47 d are not provided with reductiongrooves. Instead, the outer edge region 45 d is provided with fourspaced-apart, identical reduction grooves 52 that pass through theentire impeller blade 1 d and are disposed next to each other. In thisembodiment, the reduction grooves 52, which form flow channels, arelocated in the outer edge portion 51 only and have a radial depth thatis substantially equal to depth T. Their width is also substantiallyequal to height A so that the cross-sectional area of a reduction groove52 is thus equal to the cross-sectional area of a reduction groove 52shown in FIGS. 4 and 5. The reduction grooves 52 have a rectangularcross-section and are radially outwardly open. They have an identicaldistance from each other. The impeller blades 1 d are designedsymmetrically relative to the plane X. This design reduces gasturbulence structures at the trailing side as well. As far asdimensioning and shape of the reduction grooves 52 are concerned,reference is made to the first embodiment. Instead of the four reductiongrooves 52, only one central reduction groove 52 may be provided.However, each impeller blade 1 d may also be provided with two or threeor even more reduction grooves 52, which should then also be disposed ina preferably symmetrical manner. Instead of the rectangular shape shownhere, other shapes are applicable as well, such as a semi-circularshape.

The following is a description of a sixth embodiment of the invention bymeans of FIGS. 14 and 15. Identical parts are referred to with the samereference numerals as the third or fifth embodiments, respectively,shown in FIGS. 8 and 9 as well as FIGS. 12 and 13 to the description ofwhich reference is made. Parts that are different in design but have thesame function are denoted by the same reference numerals with asubsequent e. This impeller 2 e has impeller blades 1 e which aresubstantially a combination of the impeller blades 1 b and 1 d shown inFIGS. 8, 9 and 12, 13. In this embodiment, each impeller blade 1 e hasthree spaced-apart reduction grooves 52 disposed one above the other ineach lateral edge region 47 b and four spaced-apart reduction grooves 52disposed in succession in the radial outer edge region 45 d of theimpeller blade. As far as dimensioning, position and shape of thereduction grooves 52 are concerned, reference is made to the first,third and fifth embodiments. In this embodiment, each of the free edgeregions 45 d, 47 b is thus provided with grooves, which results in aparticularly low turbulence structure at the trailing side since aparticularly high number of reduction grooves 52 is provided and thesurfaces 48 e, 49 e are particularly small. The impeller blades 1 e areagain symmetrical relative to the symmetry plane X. Alternatively, thesemi-circular reduction grooves 52 c are also applicable in thisembodiment. Furthermore, each of the edge regions 45 d and/or 47 b maybe provided with a different number of reduction grooves 52.

An axially lateral and/or radially outer grooving of the impeller bladesreduces the front and rear surfaces thereof by forming flow channels,thus reducing turbulence structures at the trailing side. The reductiongrooves may be of any desired shape. To this end, each impeller blade isprovided with at least one reduction groove. Each of the lateral edgeregions and/or the radially outer edge regions may be provided with anydesired number of grooves. One and the same impeller blade may also beprovided with reduction grooves of different shapes. Each lateral edgeregion and/or each outer edge region is provided with at least onereduction groove, wherein the actual number of which in the respectiveedge regions may be randomly selected and may be different from one edgeregion to the next. A symmetrical design of the impeller blades or asymmetrical arrangement of the reduction grooves, respectively, ispreferred.

As an alternative to the described grooves, the lateral edge regions canalso be chamfered, in other words they can have set-back blade edges,and/or the radially outer edge regions can be chamfered as well. Thesechamfers form flow recesses again that reduce the front and/or rearsurfaces of the impeller blades so that turbulence structures at thetrailing side are reduced to a minimum. The lateral flow recesses may beoriented such that the impeller blades become larger or smaller fromtheir front surfaces towards their rear surfaces. The impeller blades orlateral edge regions, respectively, may also converge upwardly orradially outwardly, respectively, such that the outer edge portion has asubstantially trapezoidal shape, for instance. In that case, flowrecesses are thus provided both radially and laterally.

The following is a description of a seventh embodiment of the inventionby means of FIGS. 16 and 17. Identical parts are referred to with thesame reference numerals as the first embodiment to the description ofwhich reference is made. Parts that are different in design but have thesame function are denoted by the same reference numerals with asubsequent f. In all aforementioned embodiments, the impeller 2 has asingle blade ring. In this embodiment on the other hand, the impeller 2f is configured as a double blade ring with another, outer carrier ring53 which delimits the cells 44 radially outwardly and adjoins the outeredge region 45 f of the impeller blades 1 f. Otherwise, there are nomajor differences compared to the first embodiment. The individualimpeller blades 2 f are again symmetrical relative to a symmetry planeX. As in the first embodiment, each edge region 47 f of this embodimentis provided with a reduction groove 52. The reduction grooves 52 areadjacent to the corresponding edge region 46 f. As far as shape,dimensioning and position of said reduction grooves 52 are concerned,reference is made to the first embodiment. According to alternativeembodiments, each of the lateral edge regions 47 f is provided with morethan one reduction groove 52. Alternatively, the reduction grooves 52are again so designed as to have a different, for instance asemi-circular, cross-section. Again, other recesses, such as chamfers,in the edge regions 47 f are conceivable as well.

The following is a description of an eighth embodiment of the inventionby means of FIG. 18. Identical parts are referred to with the samereference numerals as the embodiment shown in FIGS. 4 and 5 to thedescription of which reference is made. Unlike the first embodiment, notall of the impeller blades 1 of this embodiment are grooved in thelateral edge regions 47 but only 30% to 70%, preferably 40% to 60%, ofall impeller blades. In this embodiment, impeller blades 1 withreduction grooves 52 according to the first embodiment are disposedbetween impeller blades without reduction grooves. The grooved impellerblades 1 are disposed randomly, i.e. stochastically. As shown at the topof FIG. 18, three regular, i.e. ungrooved impeller blades are providedbetween two grooved impeller blades 1. At the upper lateral sides on theother hand, only two regular impeller blades are provided between twogrooved impeller blades 1. It is however also conceivable to arrange twogrooved impeller blades 1 directly behind each other. In thisembodiment, the reduction grooves 52 act as reducing grooves forreducing periodic flow structures. This prevents formation of regular,harmonic flow structures, thus ensuring a particularly silent operationof the side channel compressor. Again, the gas turbulence structures atthe trailing side are reduced as well.

Instead of the impeller blades 1 described here according to theembodiment shown in FIGS. 4 and 5, the other aforementioned impellerblades are applicable as well. Also, several different impeller bladesof the aforementioned embodiments may be provided in one and the sameimpeller. Sequence repetitions are possible. Alternatively, identicallygrooved impeller blades may be provided several times in a row. Thesequence is thus completely random. What is essential is that theimpeller blades are designed differently, for instance in terms of theirshape and/or size. The impeller blades can also only differ in heightand/or width. They are preferably disposed equidistantly.

The side channel compressor may comprise at least one stationaryprojection for engaging with the at least one flow recess or reductiongroove 52, 52 c. In contrast to the at least one movable flow recess orreduction groove 52, 52 c, the at least one projection is immobile.

The interceptor 35 for the impeller 2, 2 a, 2 b, 2 c, 2 e, 2 f may haveat least one projection which projects towards the impeller 2, 2 a, 2 b,2 c, 2 e, 2 f and may engage with the at least one flow recess orreduction groove 52, 52 c in the lateral edges 47, 47 a, 47 b, 47 c, 47f of the impeller blades 1, 1 a, 1 b, 1 c, 1 e, 1 f. One projection ofthe interceptor 35 is provided for each flow recess or reduction groove52, 52 c. The interceptor 35 for the impeller 2 has one projection. Theinterceptor 35 for the impeller 2 a has two separate projections. Theinterceptors 35 for the impellers 2 b, 2 c and 2 e have three separateprojections. The interceptor for the impeller 2 f has one projection.The size and the design of the projections are adapted to the size andthe design of the flow recesses or reduction grooves 52, 52 c. There isa small play between the at least one projection and the at least oneflow recess or reduction groove 52, 52 c. The at least one projectioncounteracts with a pressure release.

According to a further embodiment, there is at least one projection onthe housing 3 which projects towards the impeller 2, 2 a, 2 b, 2 c, 2 d,2 e, 2 f and may engage with the at least one flow recess or reductiongroove 52, 52 c. The at least one projection may engage with the flowrecesses or reduction grooves 52, 52 c in the lateral edges 47, 47 a, 47b, 47 c, 47 f and/or in the head edges 45, 45 d. The size and the designof the at least one projection is adapted to the size and the design ofthe flow recesses or reduction grooves 52, 52 c.

The at least one projection may have an elongate curved form which isconcentric to the longitudinal axis 4.

1. A side channel compressor for compressing a gas comprising a) ahousing (3) b) a side channel (30) located in the housing (3) forcompressing a gas, c) a gas inlet opening (31) formed in the housing (3)which is in flow connection with the side channel (30) for introducing agas to be compressed, d) a gas outlet opening (32) formed in the housing(3) for discharging the gas to be compressed from the side channel (30),the gas outlet opening (32) being in flow connection with the gas inletopening (31) by way of the side channel (30), and e) an impeller (2; 2a; 2 b . . . ; 2 g) which is mounted for rotary drive in the housing (3)and has at least two impeller blades (1; 1 a; 1 b . . . ; 1 f) disposedin the side channel (30), wherein at least one impeller blade (1; 1 a; 1b . . . ; 1 f) has at least one flow recess (52, 52 c) in its free edgeregion (45 d; 47; 47 a; 47 b; 47 c; 47 f).
 2. A side channel compressoraccording to claim 1, wherein each impeller blade (1; 1 a; 1 b . . . ; 1f) has lateral edges (47; 47 a; 47 b; 47 c; 47 d; 47 f), wherein thelateral edges (47; 47 a; 47 b; 47 c; 47 d; 47 f) are provided with flowrecesses (52, 52 c) so as to reduce gas turbulence structures.
 3. A sidechannel compressor according to claim 2, wherein each lateral edge (47;47 a; 47 b; 47 c; 47 f) is provided with at least one flow recess (52,52 c).
 4. A side channel compressor according to claim 1, wherein eachimpeller blade (1; 1 a; 1 b . . . ; 1 f) has a head edge (45; 45 d), thehead edges (45 d) being provided with flow recesses (52; 52 c) forreducing gas turbulence structures.
 5. A side channel compressoraccording to claim 4, wherein each head edge (45 d) is provided with atleast one flow recess (52; 52 c).
 6. A side channel compressor accordingto claim 1, wherein the flow recesses (52; 52 c) are flow grooves.
 7. Aside channel compressor according to claim 1, wherein the flow recessesare flow chamfers.
 8. A side channel compressor according to claim 1,wherein at least two impeller blades (1; 1 a; 1 b . . . ; 1 f) differfrom each other so as to reduce periodic flow structures.
 9. A sidechannel compressor according to claim 8, wherein each impeller blade (1;1 a; 1 b . . . ; 1 f) has a head edge (45 d), wherein the at least twoimpeller blades (1; 1 a; 1 b . . . ; 1 f) differ in terms of their headedges (45; 45 d).
 10. A side channel compressor according to claim 9,wherein the head edges (45; 45 d) differ in terms of flow recesses (52;52 c).
 11. A side channel compressor according to claim 8, wherein theimpeller blades (1; 1 a; 1 b . . . ; 1 f) have lateral edges (47; 47 a;47 b; 47 c; 47 d; 47 f), wherein the at least two impeller blades (1; 1a; 1 b . . . ; 1 f) differ in terms of their lateral edges (47; 47 a; 47b; 47 c; 47 d; 47 f).
 12. A side channel compressor according to claim11, wherein the lateral edges (47; 47 a; 47 b; 47 c; 47 d; 47 f) differin terms of flow recesses (52; 52 c).
 13. A side channel compressoraccording to claim 8, wherein the impeller blades differ in terms oftheir size.
 14. A side channel compressor according to claim 8, whereinthe different impeller blades (1; 1 a; 1 b . . . ; 1 f) are disposed ina random sequence.
 15. A side channel compressor according to claim 1,comprising at least one stationary projection for engaging with the atleast one flow recess (52, 52 c).